Today ordinary chewing gums and bubble gums generally utilize as their gum base one or a combination of two or more natural or synthetic elastomers. The gum base that is selected provides the chewing gum with its masticatory properties. A chewing gum base is normally admixed with sugars or synthetic sweeteners, perfumes, flavors, plasticizers, and fillers; and then milled and formed into sticks, sheets, or pellets. Cottonseed oil is sometimes also added to give the gum softness. Styrene butadiene rubber (SBR) is a synthetic elastomer that is widely used as a gum base in chewing gums. However, SBR is not widely used in manufacturing soft chew gums because it lacks the desired physical properties. Polyisobutylene is widely used in manufacturing soft chew gums even though it is much more expensive than SBR.
In any case, chewing gum compositions are typically comprised of a water soluble bulk portion, a water insoluble chewing gum base portion and typically water insoluble flavoring agents. The water soluble portion dissipates with a portion of the flavoring agent over a period of time during chewing. The gum base portion is retained in the mouth throughout the chewing process.
The gum base includes a number of ingredients that are subject to deterioration through oxidation during storage. The insoluble gum base is generally comprised of elastomers, elastomer plasticizers, waxes, fats, oils, softeners, emulsifiers, fillers, texturizers and miscellaneous ingredients, such as antioxidants, preservatives, colorants and whiteners. The compounds containing carbon--carbon double bonds, such as fats, oils, unsaturated elastomers and elastomer plasticizers, are susceptible to oxidation. The gum base constitutes between 5-95% by weight of the chewing gum composition, more typically 10-50% by weight of the chewing gum, and more commonly 15-35% by weight of the chewing gum.
In chewing gum base natural or artificial antioxidants are utilized to stabilize the rubbery polymer. For instance, beta-carotenes, acidulants (e.g. Vitamin C), propyl gallate, BHA, and BHT are commonly used to stabilize the rubber used in manufacturing chewing gum. Such antioxidants are included in chewing gum base as a stabilizer to inhibit oxidation.
Antioxidants are widely used in food products susceptible to degeneration, in one form or another, due to oxidation. "Antioxidants" are defined by the Food and Drug Administration (21 CFR .sctn.170.3) as "substances used to preserve food by retarding deterioration, rancidity, or discoloration due to oxidation." Commercial applications include use in processed meat and poultry, salad dressings, seasonings, snacks, nuts, soup bases, edible fats and oils, natural foods, pet foods and packaging. In addition to foods, antioxidants have been used to prevent oxidation in various cosmetic and toiletry products and in medicinal or pharmaceutical preparations. The primary purpose in each of these applications is to prevent deterioration of desirable product characteristics by inhibiting oxidation.
More recently, antioxidants in food sources and dietary supplements have received attention for their potential to prevent or delay the onset of certain cancers and other chronic health conditions including heart disease, cataracts and aging. The theory is that, by preventing oxidation, these materials inhibit the formation of oxygen containing free radicals that are believed to play a significant role in initiation of these conditions and other chronic disorders.
The use of spices to prevent food deterioration as well as to impart flavor has been known for centuries. Because of their cost and availability, however, synthetic antioxidants, such as butyl hydroxyanisole ("BHA") and butylated hydroxytoluene ("BHT"), have been predominant in commercial food preparation. These antioxidants have proven to be quite effective. However, there is currently a desire to utilize natural antioxidants in food products and chewing gum.
There is a growing desire for chewing gum base that is stabilized with a natural stabilizer. U.S. Pat. No. 4,489,099 discloses the use of Vitamin E in combination with dilauryl thiodipropionate (DLTDP), as a stabilizer for a styrene-butadiene rubber in chewing gum. U.S. Pat. No. 5,132,121, U.S. Pat. No. 5,200,213, and U.S. Pat. No. 5,270,060 disclose a use of 0.01-1.00% by weight of a tocopherol mixture comprising 7-20% by weight alpha tocopherol, 45-75% by weight gamma tocopherol and 18-32% by weight delta tocopherol to stabilize chewing gum base.
Carnosic acid is a phenolic diterpene that corresponds to the empirical formula C.sub.20 H.sub.28 O.sub.4. It occurs naturally in plants of the Libiatae family. For instance, carnosic acid is a constituent of the species Salvia officinalis (sage) and Rosmarinus officinalis (rosemary) where it is mainly found in the leaves. Carnosic acid is also found in thyme and marjoram. It was discovered by Linde in Salvia officinalis [Helv. Chim Acta 47, 1234 (1962)] and by Wenkert et al. in Rosmarinus officinalis [J. Org. Chem. 30, 2931 (1965)]. It was then positively identified in various other species of sage, such as for example Salvia canariensis [Savona and Bruno, J. Nat. Prod. 46, 594 (1983)] or Salvia willeana [de la Torre et al., Phytochemistry 29, 668 (1990)]. It is also present in Salvia triloba and Salvia sclarea.
Carnosic acid is a powerful antioxidant [Brieskorn and Domling, Z. Lebensm. Unters. Forsch. 141, 10 (1969)] and, according to a number of Russian works where it bears the name salvine, an antibiotic against Staphylococcus aureus [CA 86, 117603r; 90, 49011b; 97, 67513r, 69163a, 69164b; 104, 221930w; 111, 130594t] and against certain microorganisms responsible for dental caries and bad breath [CA 97, 84835q]. In connection with this latter property, it is mentioned in the prior art for the production of dentifrices and mouthwashes [JP 59 103 665, Lion Corp.].
Dried leaves of rosemary or sage contain between 1.5 and 2.5% carnosic acid and about 0.3-0.4% carnosol which is also an antioxidant. Rosmanol and rosmaridiphenol are present in smaller concentrations. Accordingly, from the point of view of the economy of a production process, carnosic acid has an indisputable advantage. According to the data disclosed in U.S. Pat. No. 4,450,097 it may be calculated that the yield of rosmanol isolated from rosemary is only 0.01%.
Wenkert et al. have demonstrated that carnosol is an oxidative artifact of carnosic acid. This oxidation takes place in the presence of oxygen both after the harvesting of rosemary or sage in the leaves left to dry in air (it can be demonstrated that the freshly cut leaves of rosemary do not contain carnosol) and when the leaves are subjected to extraction with solvents or when the extracts themselves are subjected to conventional operations of fractionation, enrichment and purification. There is every reason to assume that rosmanol, which has been identified in a rosemary fraction subjected to an alkaline treatment, is itself a subsequent product of the oxidation of carnosic acid, as Wenkert et al. have suggested. The same may also be reasonably assumed of rosmaridiphenol. Carnosic acid is therefore the only phenolic diterpene present in the native state in rosemary and sage.
Some methods for the preparation of carnosic acid by chemical synthesis have also been proposed in the literature by W. L. Meyer et al. [Tetrahedron Letters 1966, 4261; 1968, 2963; J. Org. Chem. 41, 1005 (1976)]. However, the syntheses involved are long and complex and, for economic reasons, cannot be applied to an industrial process. In addition, these syntheses lead to racemic mixtures of carnosic acid precursors and not to the pure enantiomers. It should also be pointed out that these works stop at the preparation of carnosic acid precursors and omit to describe the final preparation step(s). Another method of obtaining carnosic acid has been described in the literature by Brieskorn and Domling [Arch. Pharm. 302, 641 (1969)], comprising the catalytic reduction of carnosol. Once again, the application of this process on a large scale could not be envisaged on account of the non-availability of carnosol.
U.S. Pat. No. 5,859,293 and U.S. Pat. No. 5,256,700 disclose techniques for extracting high purity carnosic acid from rosemary and sage. For example, U.S. Pat. No. 5,256,700 discloses a process for obtaining carnosic acid comprising extracting a vegetable material selected from the group consisting of sage and rosemary with an apolar solvent to obtain an extract containing apolar compounds including carnosic acid, contacting the extract with an adsorbent material having an affinity for polar compounds for adsorbing the carnosic acid to separate the carnosic acid from the apolar compounds of the extract, desorbing the adsorbent material with a polar solvent to obtain the carnosic acid in the solvent and then evaporating the polar solvent from the carnosic acid to obtain a residue containing the carnosic acid.